1. Field of the Invention
The present invention relates to a video-image processing apparatus for carrying out overdrive processing on an input video-image signal, a video-image display apparatus employing the video-image processing apparatus and a video-image display system including the video-image display apparatus.
2. Description of the Related Art
In recent years, an LCD (Liquid Crystal Display) apparatus of the active-matrix type is used widely as the image display section of a thin TV or the image display section of a portable terminal. The LCD apparatus employs a TFT (Thin Film Transistor) for each pixel of the LCD apparatus. Pixels employed in such an LCD apparatus are arranged to form a matrix including rows on the display screen of the LCD apparatus. In general, every pixel is driven by writing a video-image signal sequentially on a row-after-row basis into an auxiliary capacitor and a liquid-crystal device which are employed in the pixel in a direction from the top of the display screen to the bottom thereof.
By the way, depending on the application of the LCD apparatus, one frame period is divided into a number of sub-periods and the LCD apparatus is driven in a driving operation referred to hereafter as a time-division driving operation in order to display a video image which varies from sub-period to sub-period. A method adopted to carry out a time-division driving operation is referred to as a time-division driving method. Typical examples of an LCD apparatus adopting the time-division driving method are an LCD apparatus disclosed in documents such as Japanese Patent Laid-Open No. 2001-318363 in which a field sequential method is adopted and a 3D (3 Dimensional) image display system disclosed in documents such as Japanese Patent Laid-Open Nos. Hei 9-138384, 2000-36969 and 2003-45343 in which the so-called shutter glasses are used.
The field sequential method is a driving method, in accordance with which one frame period is divided into three frame sub-periods allocated to operations to sequentially write R (red), G (green) and B (blue) video-image signals respectively into pixels. In addition, in accordance with the field sequential method, the R, G and B light rays are emitted from a backlight synchronously with the R, G and B video-image signals respectively. In an ordinary LCD apparatus, a pixel is generally divided into R, G and B sub-pixels which are laid out spatially. Thus, the efficiency of the utilization of light is poor. By adopting the field sequential driving method, however, the efficiency of the utilization of light can be improved.
In the 3D image display system making use of shutter glasses, on the other hand, one frame period is divided into two frame sub-periods allocated to operations to alternately display two video images provided for the left and right eyes respectively as images having a disparity recognized by the left and right eyes. The 3D image display system makes use of shutter glasses which are switched to close the left eye and open the right eye and vice versa synchronously with the operations to alternately display the two video images provided for the left and right eyes. The viewer views a displayed image by wearing the switched shutter glasses which allow the image to be seen by the viewer as a 3D image.